With the demand for multimedia services of high quality in a wireless communication environment, there has been a need for a wireless transmission technique that delivers massive data at a higher rate and a lower error rate.
In order to achieve higher data transmission rates, a multi-band antenna system has been proposed. Generally, a multi-band antenna system includes a plurality of antennas, a plurality of band pass filters (BPFs), and a plurality of radio frequency (RF) circuits. Each antenna transmits and/or receives signals in different frequency bands, and each BPF and RF circuit processes signals transmitted and received through each antenna. However, use of a plurality of antennas is necessarily required which may increase the size of the antenna system.
In a multiple-input multiple-output (MIMO) antenna, an MIMO operation is carried out by arranging a plurality of antennas in a specific structure. Accordingly, it is possible to increase the data transfer rate in a specific range or expand a system range for a specific data transfer rate.
A MIMO antenna, which is believed to be the next-generation mobile communication technique applicable to mobile terminals and repeaters far and wide, is attracting attention as a new solution to overcome the limited transmission quantity of the mobile communications and wireless communication devices. It is believed that a MIMO antenna will allow for high speed broadband communication, high bandwidth, improved communication range, and high mobility. A MIMO antenna may be operated in broad or multiple frequency bands and may also improve data transmission rate between wireless communication devices.
Generally, a plurality of antennas having the same capability is embodied in a MIMO antenna. To install the MIMO antenna in a small terminal, the interval between the antennas may be narrowed. However, electromagnetic waves radiated from the antennas may interfere with each other in that situation.
The antennas may be spaced from each other at a predetermined interval, or additional devices such as a slit may be mounted to the MIMO antenna to prevent the interference between the antennas.
However, it has been difficult to reduce the interference between the antennas despite the antennas being spaced from each other at a predetermined interval.
Furthermore, the size of the MIMO antenna is increased due to the presence of the predetermined interval or the additional devices.